Change device dashboard to use MQTT

examples/device-dashboard/net.c

@@ -0,0 +1,170 @@
+// Copyright (c) 2020-2022 Cesanta Software Limited
+// All rights reserved
+
+#include "mongoose.h"
+
+#define MQTT_SERVER "mqtt://broker.hivemq.com:1883"
+#define MQTT_PUBLISH_TOPIC "mg/my_device"
+#define MQTT_SUBSCRIBE_TOPIC "mg/#"
+
+// Authenticated user.
+// A user can be authenticated by:
+//   - a name:pass pair
+//   - a token
+// When a user is shown a login screen, she enters a user:pass. If successful,
+// a server returns user info which includes token. From that point on,
+// client can use token for authentication. Tokens could be refreshed/changed
+// on a server side, forcing clients to re-login.
+struct user {
+  const char *name, *pass, *token;
+};
+
+// This is a configuration structure we're going to show on a dashboard
+static struct config {
+  char *url, *pub, *sub;  // MQTT settings
+} s_config;
+
+static struct mg_connection *s_mqtt = NULL;  // MQTT connection
+
+// Try to update a single configuration value
+static void update_config(struct mg_str *body, const char *name, char **value) {
+  char buf[256];
+  if (mg_http_get_var(body, name, buf, sizeof(buf)) > 0) {
+    free(*value);
+    *value = strdup(buf);
+  }
+}
+
+// Parse HTTP requests, return authenticated user or NULL
+static struct user *getuser(struct mg_http_message *hm) {
+  // In production, make passwords strong and tokens randomly generated
+  // In this example, user list is kept in RAM. In production, it can
+  // be backed by file, database, or some other method.
+  static struct user users[] = {
+      {"admin", "pass0", "admin_token"},
+      {"user1", "pass1", "user1_token"},
+      {"user2", "pass2", "user2_token"},
+      {NULL, NULL, NULL},
+  };
+  char user[256], pass[256];
+  struct user *u;
+  mg_http_creds(hm, user, sizeof(user), pass, sizeof(pass));
+  if (user[0] != '\0' && pass[0] != '\0') {
+    // Both user and password is set, search by user/password
+    for (u = users; u->name != NULL; u++)
+      if (strcmp(user, u->name) == 0 && strcmp(pass, u->pass) == 0) return u;
+  } else if (user[0] == '\0') {
+    // Only password is set, search by token
+    for (u = users; u->name != NULL; u++)
+      if (strcmp(pass, u->token) == 0) return u;
+  }
+  return NULL;
+}
+
+// Notify all config watchers about the config change
+static void send_notification(struct mg_mgr *mgr, const char *name,
+                              const char *data) {
+  struct mg_connection *c;
+  for (c = mgr->conns; c != NULL; c = c->next) {
+    if (c->label[0] == 'W')
+      mg_http_printf_chunk(c, "{\"name\": \"%s\", \"data\": %s}", name, data);
+  }
+}
+
+// Send simulated metrics data to the dashboard, for chart rendering
+static void timer_metrics_fn(void *param) {
+  char buf[50];
+  mg_snprintf(buf, sizeof(buf), "[ %lu, %d ]", (unsigned long) time(NULL),
+              10 + (int) ((double) rand() * 10 / RAND_MAX));
+  // MG_INFO(("%s", buf));
+  send_notification(param, "metrics", buf);
+}
+
+// MQTT event handler function
+static void mqtt_fn(struct mg_connection *c, int ev, void *evd, void *fnd) {
+  if (ev == MG_EV_MQTT_OPEN) {
+    struct mg_str topic = mg_str(s_config.pub);
+    mg_mqtt_sub(s_mqtt, &topic, 1);
+  } else if (ev == MG_EV_MQTT_MSG) {
+    struct mg_mqtt_message *mm = evd;
+    char buf[256];
+    snprintf(buf, sizeof(buf), "{\"topic\":\"%.*s\",\"data\":\"%.*s\"}",
+             (int) mm->topic.len, mm->topic.ptr, (int) mm->data.len,
+             mm->data.ptr);
+    send_notification(param, "message", buf);
+  } else if (ev == MG_EV_CLOSE) {
+    s_mqtt = NULL;
+  }
+}
+
+// Keep MQTT connection open - reconnect if closed
+static void timer_metrics_fn(void *param) {
+  struct mg_mgr *mgr = (struct mg_mgr *) param;
+  if (s_mqtt == NULL) {
+    struct mg_mqtt_opts opts = {};
+    s_mqtt = mg_mqtt_connect(mgr, s_config.rl, &opts, mqtt_fn, NULL);
+  }
+}
+
+// HTTP request handler function
+void device_dashboard_fn(struct mg_connection *c, int ev, void *ev_data,
+                         void *fn_data) {
+  if (ev == MG_EV_OPEN && c->is_listening) {
+    mg_timer_add(c->mgr, 1000, MG_TIMER_REPEAT, timer_metrics_fn, c->mgr);
+    mg_timer_add(c->mgr, 1000, MG_TIMER_REPEAT, timer_mqtt_fn, c->mgr);
+    s_config.url = strdup(MQTT_SERVER);
+    s_config.pub = strdup(MQTT_PUBLISH_TOPIC);
+    s_config.sub = strdup(MQTT_SUBSCRIBE_TOPIC);
+  } else if (ev == MG_EV_HTTP_MSG) {
+    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
+    struct user *u = getuser(hm);
+    // MG_INFO(("%p [%.*s] auth %s", c->fd, (int) hm->uri.len, hm->uri.ptr,
+    // u ? u->name : "NULL"));
+    if (mg_http_match_uri(hm, "/api/hi")) {
+      mg_http_reply(c, 200, "", "hi\n");  // Testing endpoint
+    } else if (u == NULL && mg_http_match_uri(hm, "/api/#")) {
+      // All URIs starting with /api/ must be authenticated
+      mg_printf(c, "%s", "HTTP/1.1 403 Denied\r\nContent-Length: 0\r\n\r\n");
+    } else if (mg_http_match_uri(hm, "/api/config/get")) {
+      mg_printf(c, "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n\r\n");
+      mg_http_printf_chunk(c, "{\"url\":\"%s\",\"pub\":\"%s\",\"sub\":\"%s\"}",
+                           s_config.url, s_config.pub, s_config.sub);
+      mg_http_printf_chunk(c, "");
+    } else if (mg_http_match_uri(hm, "/api/config/set")) {
+      // Admins only
+      if (strcmp(u->name, "admin") == 0) {
+        update_config(&hm->body, "url", &s_config.url);
+        update_config(&hm->body, "pub", &s_config.pub);
+        update_config(&hm->body, "sub", &s_config.sub);
+        send_notification(fn_data, "config", "null");
+        mg_printf(c, "HTTP/1.1 200 OK\r\nContent-Length: 0\r\n\r\n");
+      } else {
+        mg_printf(c, "%s", "HTTP/1.1 403 Denied\r\nContent-Length: 0\r\n\r\n");
+      }
+    } else if (mg_http_match_uri(hm, "/api/message/send")) {
+      char buf[256];
+      if (mg_http_get_var(&hm->body, "message", buf + 1, sizeof(buf) - 2) > 0) {
+        buf[0] = buf[strlen(buf)] = '"';
+        send_notification(fn_data, "message", buf);
+      }
+      mg_printf(c, "HTTP/1.1 200 OK\r\nContent-Length: 0\r\n\r\n");
+    } else if (mg_http_match_uri(hm, "/api/watch")) {
+      c->label[0] = 'W';  // Mark ourselves as a event listener
+      mg_printf(c, "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n\r\n");
+    } else if (mg_http_match_uri(hm, "/api/login")) {
+      mg_printf(c, "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n\r\n");
+      mg_http_printf_chunk(c, "{\"user\":\"%s\",\"token\":\"%s\"}\n", u->name,
+                           u->token);
+      mg_http_printf_chunk(c, "");
+    } else {
+      struct mg_http_serve_opts opts = {0};
+#if 0
+      opts.root_dir = "/web_root";
+      opts.fs = &mg_fs_packed;
+#else
+      opts.root_dir = "web_root";
+#endif
+      mg_http_serve_dir(c, ev_data, &opts);
+    }
+  }
+}